DE102017120775B4 - Method of controlling an internal combustion engine variable valve timing of a hybrid electric vehicle - Google Patents

Abstract

A method of controlling an engine variable valve timing of a hybrid electric vehicle, the method comprising:selecting (S13-S15) one of the fuel efficiency prioritized intake/exhaust cam control mode and the normal intake/exhaust cam control mode, characterized in that the method further comprises providing a cam position adjustment table of a fuel efficiency prioritized intake/exhaust cam control mode to improve fuel efficiency and a cam position adjustment table of a normal intake/exhaust Cam control mode for improving vacuum performance of an internal combustion engine, wherein the cam position setting table of the fuel efficiency prioritized intake/exhaust cam control mode differs from the cam position setting table of the normal intake/exhaust cam control mode is,selecting (S13-S15) one of the fuel-efficiency-prioritized intake/exhaust cam control mode and the normal intake/exhaust cam control mode is according to a canister charge amount and according to whether position diagnosis of a intake cam and position diagnosis of an exhaust cam are completed, wherein the canister charge amount is an amount of fuel vapor trapped in a canister, and the method further comprises determining (S17, S20) position control values of the intake cam and the exhaust cam by using the cam position setting table of the selected control mode and then controlling (S18, S21) positions of the intake cam and the exhaust cam according to the determined position control values.

Description

Background of the Invention

field of invention

The present invention relates to an engine variable valve timing control method (e.g., a method for controlling an engine variable valve opening/closing timing) of a hybrid electric vehicle, more particularly to an engine variable valve timing control method of a hybrid electric vehicle , which enables control of an intake/exhaust cam for improving the fuel efficiency of the vehicle while ensuring a canister vent amount and addressing an issue called on-board diagnostics (OBD). regards.

Description related technique

An internal combustion engine generates power by drawing fuel and air into a combustion chamber and burning them.

When the air is sucked in, the intake cams are actuated by driving a camshaft, and air is sucked into the combustion chamber through an intake passage while the intake valves are opened.

Further, exhaust valves are actuated by driving the camshaft, and gas is discharged from the combustion chamber to the outside through an exhaust passage while the exhaust valves are opened.

Meanwhile, the optimum intake and exhaust valve opening and closing timing and intake and exhaust valve opening durations depend on operating conditions such as engine rpm and engine load .

That is, the adequate valve opening and closing timing depends on the rpm of the internal combustion engine.

Accordingly, a technique of retarding or advancing the valve opening/closing timing has been introduced, and combustion efficiency can be improved by adjusting the valve opening/closing timing in accordance with the operating conditions of the internal combustion engine.

Accordingly, a variable valve timing (WT) device for changing the phase at which an intake valve or an exhaust valve is opened or closed is used as one Device for realizing an adequate valve actuation according to the operating conditions of the internal combustion engine.

The above makes it possible to optimally control the valve opening and closing timing by changing the phase of the camshaft and the phase of the valves with respect to the crankshaft by rotating the camshaft from a low speed (e.g. speed) to for optimal valve timing high speed (e.g., speed), thereby improving fuel efficiency, reducing exhaust emissions, increasing low-speed torque, and improving engine output.

That is, in an internal combustion engine to which the WT device is applied, the valve overlap of the intake and exhaust valves can be improved to reduce pumping loss, and therefore fuel efficiency can be improved according to the decrease in pumping loss.

Further, since it is possible to optimize the valve overlap according to the engine operating conditions, the exhaust gas can be reduced by the effect of reburning the unburned gas by means of the internal exhaust gas recirculation (EGR).

Moreover, since volumetric efficiency can be improved by optimizing the timing (e.g., open/close timing) of the intake valve, the low-speed torque can be increased and the engine output can be increased.

For example, in the case of WT control for assisting the engine output in an engine to which the VVT device is applied, the valve overlap is increased by advancing the intake and exhaust cams in the full load and high -Load range of the combustion engine to improve the intake performance of the combustion engine.

Furthermore, in the low load range, the intake and exhaust cams are retarded to reduce valve overlap and ensure engine inactivity and fuel efficiency control performance.

In the medium-load condition, the VVT control is performed considering management of the fuel efficiency and the balance range of the power delivery.

When the intake and exhaust cams are advanced, the valve overlap is increased. As valve overlap increases, engine negative pressure increases and engine output increases.

On the contrary, when the intake/exhaust cam is controlled to be at a retarded (not advanced) position, the valve overlap decreases. As the valve overlap decreases, the engine negative pressure decreases and the engine output power decreases.

The VVT technique for controlling the position of the intake and exhaust camshafts according to the operating conditions of the engine is also applied to a hybrid electric vehicle using an engine and an electric motor as the vehicle drive sources.

That is, after the driver-required torque is determined from the vehicle running information and status information, and the engine torque and the motor torque that satisfy the driver-required torque are also determined when a camshaft position control value is off the determined engine torque (or the intake air amount) and the current engine revolution number value, the position of the intake/exhaust camshaft is controlled by operating the actuator of the VVT device according to the determined position control value.

Here, the position control value of the intake/exhaust cam is determined by setting data (table or map) in the engine control unit (ECU) in which the advanced position of the intake/exhaust cam cam is predetermined for engine torque and engine speed.

Meanwhile, the control value set in the setting data or the intake/exhaust camshaft position setting value is limited for OBD and control of the intake negative pressure of the engine.

Here, control of the intake negative pressure of the internal combustion engine is necessary for canister purge control for evaporative gas regulation.

When the intake/exhaust cam of the hybrid-electric vehicle is controlled to be at the maximum retarded position (i.e. the position at which the cam is not advanced) to improve fuel efficiency in the normal operating range except for a certain range ( a full-load range), the output insufficient for driver-required torque is compensated with the electric motor assist, fuel efficiency can be improved, and engine vacuum generation is reduced. Therefore, during driving in the US federal test procedure (FTP) certified mode, because the amount of canister venting is insufficient according to a decrease in negative pressure, the evaporative gas regulation will not is met or the WT diagnosis condition is not met or onboard diagnostics (OBD) diagnosis is impossible.

From the DE 10 2013 204 094 A1 a method according to the preamble of claim 1 is known. From the DE 10 2005 003 006 B4 discloses a variable valve timing diagnosis system capable of performing position diagnosis of an intake cam and position diagnosis of an exhaust cam.

The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an admission or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art .

Explanation of the invention

The object of the present invention is to provide a control method for engine variable valve timing of a hybrid electric vehicle, which enables control of the intake/exhaust cam to improve the fuel efficiency of the vehicle while ensuring the canister purge amount and the start-up of a problem affecting OBD diagnostics.

This object is solved by a method for controlling an internal combustion engine variable valve timing of a hybrid electric vehicle according to claim 1. Further developments are subject of the dependent claims.

According to the present invention, there is provided a method of controlling an engine variable valve timing of a hybrid-electric vehicle, comprising: ready prepare a cam position setting table of a fuel efficiency prioritized intake/exhaust cam control mode to improve fuel efficiency and a cam position setting table of a normal intake/exhaust cam control mode to improve engine vacuum performance, wherein the fuel efficiency prioritized intake/exhaust cam timing mode cam position adjustment table is distinguished from the normal intake/exhaust cam timing mode cam position adjustment table, selecting (eg, accurate) one of the fuel efficiency -prioritized-intake/exhaust cam control mode and the normal intake/exhaust cam control mode according to a canister loading amount and whether or not the diagnosis of an intake cam and the diagnosis of an exhaust cam are completed, the canister charge amount is an amount of fuel vapor trapped in a canister and determining intake cam and exhaust cam position control values using the cam position adjustment table of the selected control mode and then controlling positions of the intake cam and the exhaust cam according to the determined position control values.

Other aspects and exemplary embodiments of the invention are discussed below.

It is to be understood that the terms "vehicle" or "vehicle-..." or other similar term used herein includes not only motor vehicles in general, which includes passenger vehicles including sport utility vehicles (SUVs), buses, trucks, numerous commercial vehicles, as well as watercraft including a variety of boats and ships, aircraft, but also hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels made from resources other than petroleum) . A hybrid vehicle, as referred to herein, is a vehicle that has two or more sources of power, including a gasoline-powered vehicle and an electric-powered vehicle.

The methods of the present invention have other features and advantages that will be apparent from or set forth in more detail in the accompanying drawings incorporated herein and the following detailed description, which together serve to explain certain principles of the present invention.

character list

• 1 Fig. 14 is a flowchart showing a variable valve timing control process according to the related art.
• 2 Fig. 14 is a flowchart showing a variable valve timing control method.
• 3 12 is a view schematically showing a cam position setting table of a fuel-efficiency prioritized intake/exhaust cam control mode, and
• 4 12 is a view schematically showing a cam position setting table of a normal intake/exhaust cam control mode.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features that explain the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the different figures of the drawing.

Detailed description

Reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. Although the invention will be described in connection with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the example embodiments, but also various alternatives, modifications, alterations and other embodiments as may be included within the scope of the invention as defined by the appended claims.

Furthermore, in the description of the present invention, a detailed description of related art and the like is omitted when it is found that it makes the subject matter of the present invention unclear.

Throughout the specification, when an element is referred to as "comprising" an element, the element may include, rather than exclude, the other elements, unless specifically stated otherwise.

Various embodiments of the present invention relate to a variable valve timing control method of an internal combustion engine configured to improve fuel efficiency of a hybrid electric vehicle.

Various aspects of the present invention are directed to providing a control method for internal combustion engine variable valve timing of a hybrid electric vehicle, which enables control of an intake/exhaust cam for improving fuel efficiency of the vehicle while ensuring a canister purge amount and the Addressing an issue affecting OBD diagnostics.

First, a variable valve timing control method of a hybrid electric vehicle according to the related art will be described in order to facilitate understanding of the present invention.

In general, the variable valve timing (or variable valve opening/closing timing) (VVT) control of the internal combustion engine, that is, the position control of the intake/exhaust cam , performed by coordinated control performed by a plurality of control units in a vehicle.

As in 1 As shown, a hybrid control unit (HCU), which is the top-level control unit, receives vehicle driving information and status information including battery state of charge (SoC) ) received from the battery management system (BMS), the current vehicle speed detected by a vehicle speed detection device, and a current accelerator pedal value (accelerator pedal position sensor (APS , from "accelerator position sensor") value) detected by means of an APS (S1), and determines the total required torque required in the vehicle based on the received vehicle running information and the status information ( S2).

Further, the HCU obtains an engine torque (torque required by the engine) and a motor torque (torque required by the motor) that satisfy the total required torque (S3).

Currently, an engine torque is determined according to the optimal operating point, and in combination with the engine torque, a motor torque that satisfies the required torque is determined.

When the engine torque is detected, the engine control unit (ECU) receives the engine torque from the HCU through CAN communication and controls the engine throttle (e.g. throttle plate) and position of the intake/exhaust cam in accordance with the engine torque received from the ECU.

Currently, the ECU determines a control value (desired camshaft position value) that controls the intake/exhaust cam position (camshaft position) to be a value related to the determined engine torque (or intake air quantity) and the current engine revolution number in the embedded setting data (table or map) corresponds (S4), and controls the actuator (e.g. the actuator) of the VVT device according to the determined control value to adjust the position of the intake/exhaust cam to control (S5).

Further, the HCU generates and outputs a command value corresponding to the motor torque, and the motor control unit (MCU) controls the operation of the motor in accordance with the motor torque command , which is output from the HCU (S5).

The position of the intake/exhaust cam may mean the positions of the intake camshaft and the exhaust camshaft provided with cams for opening and closing the intake valve and the exhaust valve, respectively, and controlling the position of the intake /Exhaust cams may include controlling intake camshaft position and exhaust camshaft position.

“Inlet/Outlet-” means both inlet and outlet. Therefore, "intake/exhaust cam" refers to both the intake cam and the exhaust cam, and "intake Zexhaust camshaft" refers to both the intake camshaft and the exhaust camshaft.

In the conventional intake/exhaust cam control mode, the control value predetermined in the setting data, that is, the target value of the intake/exhaust camshaft position, is limited in terms of OBD diagnosis and engine intake negative pressure control .

Here, control of the intake negative pressure of the internal combustion engine is necessary for the canister purge control that is arranged to cope with evaporative gas regulation.

Therefore, considering the above, the present invention adds a fuel-efficiency prioritized intake/exhaust cam control mode as one of the internal combustion engine variable valve timing (WT) control modes, and when the fuel-efficiency prioritized intake/exhaust Exhaust cam control mode is performed, the engine output is reduced and control is performed to further compensate for the reduced engine output accordingly with electric motor assistance.

The fuel efficiency prioritized intake/exhaust cam control mode is configured to adjust the intake/exhaust cam control position (camshaft position control value) to improve fuel efficiency by avoiding the constraint involved in adjusting the intake/exhaust Exhaust cam timing position is raised.

Moreover, the fuel-efficiency-prioritized intake/exhaust cam control mode is a mode that expands the operating range in which the position of the intake cam (intake camshaft position) is fixed to a retarded position to maximize improvement of fuel efficiency. In the present mode, all intake cam positions are fixed to retarded positions in the operating range except for the high load (high torque) range, which has torques not lower than a target torque, and the high speed (high -RPM range) that has speeds not lower than a target speed (RPM).

However, in the fuel efficiency prioritized intake/exhaust cam control mode, it is not an optimal control condition to control the position of the exhaust cam (exhaust camshaft position) to a retarded position in terms of fuel efficiency and exhaust emissions, and hence the position of the exhaust cam is controlled to a preferred position in terms of fuel efficiency and exhaust emissions.

Currently, a separate exhaust cam position setting table or map different from that of the normal intake/exhaust cam control mode, which will be described later, is predetermined and the position control value of the exhaust cam is estimated using the exhaust cam position adjustment table or map above. Then, the position of the exhaust cam is controlled with the estimated position control value being set as a target value.

The present fuel-efficiency-prioritized-intake/exhaust-cam control mode can be particularly considered as a mode in which fuel efficiency is prioritized even when the negative pressure performance and the output performance of the internal combustion engine are slightly lowered because the operating range in which the intake cam is fixed to a retarded position without advancing the intake cam is significantly enhanced compared to the conventional intake/exhaust cam control mode.

Further, the variable valve timing (WT) logic is configured to control the position of the intake/exhaust cam differently according to the conditions.

In other words, the fuel-efficiency-prioritized-intake/exhaust cam control mode is set to be performed only when a predetermined mode-entry condition is met, and the ECU determines whether to enter the fuel-efficiency-prioritized intake /exhaust cam control mode to enter and execute.

When the set (eg, set) entry condition is not met, an intake/exhaust cam control mode is performed to control the position of the intake/exhaust cam with a control value determined according to engine torque (or the intake air amount) and the engine revolution number.

The present mode is a control mode different from the fuel-efficiency-prioritized intake/exhaust cam control mode, and is hereinafter referred to as “normal intake/exhaust cam control mode”.

With the addition of the fuel efficiency prioritized intake/exhaust cam control mode, the internal combustion engine variable valve timing control mode points to the fuel efficiency prioritized intake/exhaust cam control mode in which the intake cam is not advanced in the extended operating range to improve fuel efficiency, and the normal intake s/exhaust cam control mode that controls the position of the intake/exhaust cam with a control value according to the engine torque (intake air amount) and the engine revolution number.

In other words, various aspects of the present invention are directed to providing two variable valve timing control modes selected according to the conditions: fuel efficiency prioritized intake/exhaust cam control mode and normal intake/exhaust cam control mode , and variable valve timing control is performed in a selected one of the two modes.

2 14 is a flow chart illustrating a variable valve timing control method implemented under coordinated control of the HCU and the ECU. In the following description, the operations performed by the two control units of the HCU and the ECU are discussed separately, but the variable valve timing control method can be implemented using an integrated control unit that integrally performs the control functions of the HCU and the ECU.

Moreover, since engine output insufficient for performing the fuel-efficiency-prioritized intake/exhaust cam control mode is additionally compensated with motor assist, control of a motor control unit (MCU) for controlling motor- Output power according to an electric motor torque command generated and output by the HCU is required for output compensation (e.g., output power compensation) by the electric motor assist, and a BMS is also included in the control method because the battery SoC (state of charge) Information is needed to determine the required torque in the hybrid electric vehicle.

As in 2 shown, the HCU first receives vehicle driving information and status information including the battery SoC, the current vehicle speed, and the accelerator pedal value (S11), and determines a total required torque (a driver required torque) which from the Vehicle is required (S12) from the received vehicle driving information and status information.

In addition, the ECU determines whether the canister charge amount is less than a predetermined reference value, and whether the diagnosis of the intake cam and the diagnosis of the exhaust cam are both completed (S13).

The reference value is a value which is determined from the previous test and evaluation process and which is input to the ECU.

When the purge flow rate is estimated using the values of variables of the operating state, which is the control duty value of a purge control solenoid valve (PCSV) and the purge -canister pressure, the combustion gas can be detected using an air-fuel ratio signal output in response to the oxygen detector, in addition to the vent flow rate.

Moreover, since various methods of determining or obtaining the box loading amount information are known, a method of determining or obtaining the box loading amount is not particularly limited in an exemplary embodiment of the present invention.

Since the canister charge amount is variable information which is already used for the on-vehicle control, and the method for detecting or obtaining the canister charge amount, which detects the canister charge amount from the purge flow rate and the air-fuel has ratio information corresponds to a known technology, a detailed description thereof will be omitted.

When both of the above conditions are satisfied, that is, when it is determined that the value of the canister loading amount is less than the reference value and the intake cam diagnosis and the exhaust cam diagnosis are all completed, the ECU selects the fuel efficiency prioritized intake/exhaust cam control mode as the variable valve timing control mode.

In other words, the above conditions are conditions for entering the fuel efficiency prioritized intake/exhaust cam control mode, and the fuel efficiency prioritized intake/exhaust cam control mode is entered only when the above conditions are met are.

The canister loading amount means a captured amount of a gaseous fuel containing hydrocarbons currently trapped in the canister. When the canister loading amount is greater than or equal to a reference value, a large amount of the gaseous fuel components exceeding the reference value is adsorbed to the activated carbon in the canister, and therefore there is a large one Probability that the purge operation is performed using the negative pressure of the engine by opening the purge control valve or the PCSV.

As is well known, in an internal combustion engine equipped with a canister, the fuel vapor generated in the fuel canister is collected in the canister and the Purge Control Solenoid Valve (PCSV) is opened during engine operation with the fuel, collected in the canister is vented to the engine intake side and then burned in the engine.

In the fuel-efficiency-prioritized intake/exhaust cam control mode, since the position of the intake cam is fixed at a retarded position (i.e., the intake cam is not advanced), in many Operating ranges except in the high speed range and the high load range, the opening degree of the throttle valve is increased to take in the same amount of air.

Currently, because the force of drawing air into the combustion chamber, namely negative pressure, is reduced, the air charging efficiency of the combustion chamber is reduced (the amount of air required for combustion is not normally provided). Thus, the engine output decreases and the canister purging performance is lowered.

In the fuel-efficiency-prioritized intake/exhaust cam control mode, the reduced amount of engine output power is compensated with electric motor assistance, but such compensation may result in reduction of canister venting performance.

Sufficient engine vacuum is required for venting operation. Accordingly, when the value of the charge amount of the canister is greater than or equal to the reference value, there is a certain probability of the purge operation, and therefore entry into the fuel-efficiency prioritized intake/exhaust cam control mode is prohibited (e.g., prohibited). Accordingly, entry into the fuel-efficiency prioritized intake/exhaust cam control mode is permitted only when the charge amount is less than the reference value.

In the normal intake/exhaust cam control mode, which is performed when the canister charge amount is greater than or equal to the reference value, since the position of the camshaft is controlled with a control value according to the operating condition of the engine that uses the WT Device used, the throttle valve (e.g. the throttle valve) can be opened normally, the engine negative pressure can be increased, and the engine output performance and the canister ventilation performance can be improved compared to the fuel-efficiency-prioritized intake/exhaust -Cam control mode.

The intake cam diagnosis process and the exhaust cam diagnosis process are normal diagnosis processes of diagnosing the responsiveness of the VVT device by checking whether the position of the actual camshaft is shifted to a position corresponding to the control value when the position of the camshaft is shifted with a predetermined control value by controlling the operation of the actuator.

Since the intake cam diagnostic procedure and the exhaust cam diagnostic procedure are known procedures that are already performed in a manner of diagnosing the responsiveness of the VVT device in accordance with predetermined diagnostic logic in one Internal combustion engine to which a WT device is applied, a detailed description of the operations and the corresponding method will be omitted.

The intake cam diagnosis and the exhaust cam diagnosis have an operation of controlling the actuator of the VVT device to advance the intake/exhaust cam position, and therefore it is difficult to determine the intake cam diagnosis and perform the exhaust cam diagnosis while performing the fuel efficiency prioritized intake/exhaust cam control mode in which the cam position is fixed to a retarded position in many operating ranges.

Therefore, intake cam diagnostics and exhaust cam diagnostics should be performed during the normal intake/exhaust cam timing mode before entering the fuel efficiency prioritized intake/exhaust cam timing mode. In particular, because the fuel efficiency prioritized intake/exhaust cam control mode should only be entered when the intake cam diagnosis and exhaust cam diagnosis are completed, the conditions for entering the fuel efficiency prioritized intake are /exhaust cam timing mode set to have a condition that the intake cam diagnosis and the exhaust cam diagnosis should be completed.

That is, it is checked whether the intake cam diagnosis and the exhaust cam diagnosis have already been completed, and the fuel efficiency prioritized intake/exhaust cam control mode can only be entered when the cam diagnosis is not required.

When the condition set by the ECU is met and entry into the fuel-efficiency prioritized intake/exhaust cam control mode is determined as described above, the ECU transmits a signal indicative of entry into the fuel-efficiency prioritized intake/exhaust cam control mode. priority intake/exhaust cam control mode notifies (S14) to the HCU which has determined the total required torque (driver required torque), and accordingly the HCU receives the signal from the ECU (S15) and determines the engine -Torque (engine required torque) and motor torque (motor required torque) based on the total required torque (S16).

When the fuel efficiency prioritized intake/exhaust cam control mode is entered, the optimum operating point is determined from the engine operating point map for the fuel efficiency prioritized intake/exhaust cam control mode and system efficiency, and the engine -Torque and the electric motor torque, which correspond to the optimal operating point, are determined.

On the other hand, in the normal intake/exhaust cam timing mode that does not satisfy the conditions set in step S13, the optimal operating point is determined from the engine operating point map for the normal intake/exhaust cam timing mode and system efficiency, and the engine torque and the motor torque, which correspond to the optimal operating point, are determined (S19).

The engine operating point map for the fuel-efficiency-prioritized intake/exhaust cam control mode has an engine torque value set to a relatively small value under the same operating condition compared to the engine operating point map that used in the normal intake/exhaust cam timing mode.

Therefore, the engine torque value determined using the engine operating point map for the fuel-efficiency prioritized intake/exhaust cam control mode is determined to be a smaller value than in the normal intake/exhaust cam control mode. Exhaust cam control mode under the same operating conditions.

On the other hand, since all the required torque (driver required torque) should be satisfied by means of the engine torque and the motor torque, the motor torque is determined to be a larger value than in the normal intake/exhaust cam -Control mode under the same operating conditions.

In the present manner, in the fuel-efficiency-prioritized intake/exhaust cam control mode, the reduced amount of engine output power is compensated with the motor assist according to the reduction in engine torque determined by the HCU.

That is, by increasing the motor torque in proportion to the reduced amount of engine torque to meet the required torque, the HCU increases the motor output. As a result, by compensating for the reduced engine output using the motor output, torque required by the driver can be output.

As described above, the operating point map for determining the engine torque is distinguished between the fuel-efficiency-prioritized intake/exhaust cam timing mode and the normal intake/exhaust cam timing mode, and therefore the engine torque and the electric motor torque is determined differently depending on the selected mode.

Furthermore, as will be described later, the ECU inherent setting data having a predetermined intake/exhaust cam position control value, namely, the intake/exhaust cam position setting table or map containing a cam Having the position control value set according to the engine torque (or the intake air amount) and the engine revolution number is also distinguished between the two modes.

The ignition timing, which is determined according to the engine RPM, intake air amount, cam position, etc., also varies between the two modes because the cam position of the engine is determined differently depending on the mode even under the same operating conditions.

Here, the ECU's own setting data, that is, an ignition timing setting table or map in which the ignition timing is predetermined according to the engine revolution number, intake air amount, cam position, etc., can also be divided into the two modes .

When the HCU receives the mode entry signal or the signal indicative of a selected mode, the HCU determines the engine torque and the motor torque corresponding to the selected mode (S13, S14-S16 and S19). Then, when the HCU transmits the determined engine torque and motor torque to the ECU and the MCU as command values, the ECU controls the engine drive and the engine output according to the engine torque command, and the MCU drives the motor drives and controls the motor output according to the motor torque command (S18, S21).

Moreover, the ECU obtains the position command value (target position value) of the intake/exhaust cams from the intake/exhaust cam position setting table (or map) of the corresponding mode based on the engine torque received from the HCU and the current engine revolution number detected by the engine revolution number detection unit (S17, S20), and then actuates the actuator of the VVT device according to the control value to adjust the position of the intake /exhaust cam (S18, S20).

Here, in the fuel-efficiency prioritized intake/exhaust cam control mode, the position control value of the intake/exhaust cam is found from the fuel-efficiency prioritized intake/exhaust cam position setting table (see 3 ) (S17). In the normal intake/exhaust cam control mode, on the other hand, the position control value of the intake/exhaust cam is selected from the normal intake/exhaust cam position setting table (see 4 ) determined (S20).

3 12 is a view schematically showing a cam position adjustment table of the fuel efficiency prioritized intake/exhaust cam control mode, and 4 14 is a view schematically showing a cam position setting table in a normal intake/exhaust cam control mode.

As shown in the figures, the cam position adjustment table of each mode allows the position of the intake/exhaust cam to be calculated from the engine torque determined by the HCU and the current engine RPM determined by the HCU of the engine revolution number detection device is detected.

In the fuel efficiency prioritized intake/exhaust cam control mode cam position setting table shown in 3 As shown, the target position of the intake cam is fixed to a retarded position in the remaining operating range (range under a target torque and a target speed) which includes the high load range (high torque range) above a target torque and excludes the high speed range (high rpm range) above a target rpm.

At present, unlike the intake cam, the position of the exhaust cam is not fixed to a retarded position in the operating range described above, but can be set to a position different from the position used in the normal intake /exhaust cam control mode is set even given the same engine torque and engine revolutions per minute.

In the fuel-efficiency-prioritized-intake/exhaust cam control mode, the position of the intake/exhaust cam can be controlled according to the engine torque and the engine revolution number in the high-load range and the high-speed range except for the above-described operating range (the operating range in which the intake cam is fixed at a retarded position). In the present case, the position of the intake/exhaust cam may be set to an advanced (or retarded) position.

Therefore, in the fuel-efficiency-prioritized intake/exhaust cam control mode, when the engine torque and the engine speed correspond to a range other than the high-load range and the high-speed range, the intake cam position is fixed at the retarded position , without being advanced.

On the other hand, the intake/exhaust cam advance control that enables an increase in the engine output can be performed, and the actuator of the VVT can be operated with a control value found from the table according to the combustion engine torque and the engine revolution number to advance the position of the intake/exhaust cam only when the engine torque and the engine revolution number correspond to the high load range and the high speed range.

In the normal intake/exhaust cam timing mode cam position setting table shown in 4 1, the control value for controlling the position of the intake/exhaust cam (including advance control) is predetermined to a value according to the engine torque and the engine revolution number.

Therefore, when the normal intake/exhaust cam control mode is selected and performed, the actuation of the actuator of the VVT device can be controlled using the position control value calculated according to the engine torque and the engine revolution number from the table is determined. Thereby, the advance control for advancing the position of the intake/exhaust cams to a position corresponding to the control value can be performed.

In the present manner, in an exemplary embodiment of the present invention, the intake/exhaust cam control may be performed in any mode selected from the fuel-efficiency-prioritized intake/exhaust cam control mode to Improving fuel efficiency and normal intake/exhaust cam control mode for improving engine vacuum performance and canister venting performance and OBD diagnosis of intake/exhaust cams according to predetermined conditions. Therefore, the fuel efficiency of the vehicle can be improved, the canister purge amount can be ensured, and an error in OBD diagnosis can be handled.

As is apparent from the above description, with a control method for engine-variable valve timing of a hybrid-electric vehicle according to an exemplary embodiment of the present invention, the control of an intake/exhaust cam can be performed in any mode selected between of a fuel efficiency prioritized intake/exhaust cam control mode to improve fuel efficiency and a normal intake/exhaust cam control mode, improvement of engine vacuum performance and OBD diagnosis of intake/exhaust cam enabled according to a predetermined condition. Therefore, a canister bleed amount and bleed performance can be secured, and a problem related to OBD diagnosis of the cam can be addressed. In addition, the fuel efficiency of the vehicle can be improved.

In particular, the control method can not only improve the fuel efficiency of the vehicle, but also has an advantage of coping with evaporative gas regulations and OBD diagnostic regulations.

For convenience of explanation and adequate definition in the appended claims, the terms "upper", "lower", "inner", "outer", "top", "bottom", "upwards", "downwards", "front" are used , "rear", "rear", "inside", "outside", "inside", "outside", "inside...", "outside...", "forward" and "backward" are used to indicate characteristics of the exemplary embodiments with reference to the locations of such features as shown in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application to enable any person skilled in the art to make and use various exemplary embodiments of the present invention, as well as alternatives and modifications thereof. It is intended that the scope of the invention be defined by the claims appended hereto.

Claims (8)

A method for controlling an engine variable valve timing of a hybrid electric vehicle, the method comprising: selecting (S13-S15) one of the fuel efficiency prioritized intake/exhaust cam control mode and the normal intake/exhaust cam control mode, characterized in that the method further comprises providing a cam position adjustment table of a fuel efficiency prioritized intake/exhaust cam control mode to improve fuel efficiency and a cam position adjustment table of a normal intake/exhaust -Cam control mode for improving vacuum performance of an internal combustion engine, the cam-position-on fuel efficiency prioritized intake/exhaust cam control mode position table is different from the cam position setting table of the normal intake/exhaust cam control mode, selecting (S13-S15) one of the fuel efficiency prioritized intake /exhaust cam control mode and the normal intake/exhaust cam control mode is performed according to a canister loading amount and according to whether position diagnosis of an intake cam and position diagnosis of an exhaust cam are completed, the canister charge amount is an amount of fuel vapor trapped in a canister, and the method further comprises determining (S17, S20) position control values of the intake cam and the exhaust cam using the cam position adjustment table of the selected control mode and then controlling (S18, S21) positions of the intake cam and the exhaust cam according to the determined position control values. procedure according to claim 1 further comprising: providing an operating point map of the fuel efficiency prioritized intake/exhaust cam control mode and an operating point map of the normal intake/exhaust cam control mode, the operating point map of the fuel efficiency prioritized intake -/exhaust cam timing mode is different from the operating point map of the normal intake/exhaust cam timing mode, determining (S13, S14-S16, S19) when a total required torque required by a vehicle is out driving information and status information about the vehicle is determined, an engine torque and an electric motor torque that satisfy the total required torque by means of the operating point map of the selected control mode, and determining (S17, S20) position control values of the intake cam and the exhaust cam corresponding to the determined engine torque and a current engine rpm using the cam position adjustment table of the selected control mode. procedure according to claim 2 , wherein the fuel efficiency prioritized intake/exhaust cam control mode operating point map is set to an engine torque less than an engine torque of the normal intake/exhaust cam control mode operating point map below same operating conditions. procedure according to claim 2 or 3 further comprising: controlling (S16), when the engine torque and the motor torque satisfying the total required torque are determined in the fuel-efficiency-prioritized intake/exhaust cam control mode, an operation of an electric motor, to output the determined electric motor torque, wherein a reduced amount of an output of the engine compared to the output in the normal intake/exhaust cam control mode is compensated by an output of the electric motor while satisfying the total required torque (S18). Method according to one of Claims 1 until 4 wherein the selecting comprises: selecting (S13-S15) the fuel efficiency prioritized intake/exhaust cam control mode when a value of the canister charge amount is less than a predetermined reference value and both the position diagnosis of the intake cam and exhaust cam position diagnosis, are completed. Method according to one of Claims 1 until 5 , wherein the cam position adjustment table of the fuel efficiency prioritized intake/exhaust cam control mode is set up in which the position control values of the intake cam are all set to a retarded position in an operating range in which the engine torque is less than a target torque and the number of revolutions per minute of an internal combustion engine is less than a target speed. Method according to one of Claims 1 until 6 wherein in the cam position setting table of the fuel efficiency prioritized intake/exhaust cam control mode, the position control values of the intake cam and the exhaust cam are set to a position value corresponding to the engine torque and the rpm of an internal combustion engine for a high load range in which an engine torque is greater than a target torque, and for a high speed range in which the rpm of the internal combustion engine is greater than or equal to a target speed, so that advance control of intake and exhaust cams is enabled. Method according to one of Claims 1 until 7 , wherein the cam position adjustment table of the fuel-efficiency-prioritized-intake/exhaust cam control mode is established by comparing the position control values of the intake cam and the exhaust cams are set to a position value corresponding to engine torque and engine rpm to enable advance control of intake and exhaust cams.

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